The invention relates to an exhaust gas system, especially for an internal combustion engine of a motor vehicle, with a nitrogen-reducing converter, an exhaust gas cleaning device and a reduction agent feed device.
WO 99/39809 A1 discloses an exhaust gas system which has arranged in the exhaust line, in the given sequence, an oxidizing converter, a particulate filter and an SCR converter for removing nitrogen oxide from the exhaust gas. Furthermore, a supply of reducing agent for feeding in ammonia or urea solution is provided on the input side of the SCR converter. With this exhaust gas system, particulates and nitrogen oxides and non-combusted fuel constituents can be removed from the exhaust gas of an internal combustion engine. Oxidation of nitrogen monoxide (NO) to nitrogen dioxide (NO2) takes place here to a greater or lesser extent, depending in each case on the exhaust gas conditions, by means of the oxidizing converter. The NO2 formed in turn oxidizes soot deposited in the particulate filter, for a continuous regeneration of the particulate filter. However, both the removal of nitrogen oxide and the removal of soot via NO2 formed are heavily dependent on the prevailing temperature conditions and throughput ratios.
It is the object of the present invention to provide an exhaust gas system for an internal combustion engine, wherein a further improvement in the cleaning of the exhaust gas, in particular over as wide an operating range as possible and during changing operating conditions of the internal combustion engine is achieved.